Treatment of liquid wastes of any kinds such as dangerous and/or radioactive organic liquids is accomplished today with thermal processes applying reactors of the oven type which may be of different natures such as static ovens or rotary ovens, heated with different means.
Thus, methods for treating wastes apply thermal units connected to gas treatment systems relatively sizeable for ensuring cooling, filtration and neutralization of certain elements such as chlorine. This is generally expressed by units of large size subjected to high temperatures. The presence of certain elements such as chlorine, phosphorus, sulfur, . . . subjected to high temperatures intensifies the corrosive properties of the gases, which forces the designers either to select super-alloys which are often very expensive, or to accept frequent replacement of certain portions of the process.
The applied reactors may be of different types. These may be ovens heated by the Joule effect, by plasma torches or by the combustion of gas fuels like propane. The treatment temperature may thus vary depending on the nature of the load. If, for example, these are hydrocarbons of the dodecane type, this load may develop a thermal power of about 10 kW per L/h, a power which has to be dissipated. If, on the other hand, this is an aqueous solution, the power of the plasma will be partly used for ensuring its vaporization. The temperature behavior of the reactor involved in the process is therefore substantially impacted by the nature of the liquid to be treated.
According to the method, the introduction of the liquids may vary. They are either introduced into the core of the hot area of the oven, or they are introduced into the power source. For example, they may be vaporized in the combustible gas or directly introduced into a plasma. They may be treated alone or as a mixture with solids depending on the case. As an example, patent application EP 469 737 proposes a method and a device for treating liquids in an air plasma [1]. In this example, the plasma burns in a reactor in a refractory material and the liquids are introduced into the gas flow generating the plasma. Such a method requires a relatively burdensome device since the produced gases have to be treated notably via washing columns.
Further, regardless of the applied method, it appears that the nature of the liquids may substantially vary for reasons of thermal releases but also for reasons of compatibility with the materials selected for making the reactor.
Several solutions to the problem of the treatment of waste involving the use of immersed plasmas have already been proposed. For example, mention may be made of the publication of N. V. Alekseev et al. relating to a treatment method in which a plasma bursts out into a container containing an aqueous solution polluted by a few tens of milligrams of phenol per liter of water [2]. In this case, the plasma is used for producing hydrogen peroxide which oxidizes the dissolved organic compounds. The publication of G. Fortin et al. also mentions a method applying an argon/nitrogen plasma torch burning at the bottom of a reactor filled with leachates loaded with cyanides [3]. An international application was moreover filed by the same authors for protecting the invention [4].
In all cases, these methods were developed for treating aqueous solutions containing small amounts of products to be removed: a few ppm of phenol in the first case, a few ppm of cyanides in the second. The products are gradually degraded by the plasma torch operating at the heart of the solution, a torch which produces chemical radicals required for oxidation of the organic compounds.
Therefore, there exists an actual need for a method for treating notably liquid chemical wastes, improved in terms of rapidity and efficiency, which may treat liquids and this, regardless of their nature and/or their composition, using a simpler, more compact and less expensive device in its achievement and/or in its use.